Powder packing methods and apparatus

ABSTRACT

The present disclosure generally relates to powder packing for additive manufacturing (AM) methods and systems. Conventional powder packing methods are manual and non-standardized, and they result in operator fatigue and potentially product inconsistencies. Powder packing according to the present disclosure improves standardization and reduces turnaround time, with the potential to lower the cost of AM.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 15/599,169,filed on May 18, 2017, titled “POWDER PACKING METHODS AND APPARATUS”,the contents of which is herein incorporated in its entirety byreference.

INTRODUCTION

The present disclosure generally relates to powder packing methods andapparatuses for use in powder-based additive manufacturing (AM) methodsand systems.

BACKGROUND

AM or additive printing processes generally involve the buildup of oneor more materials to make a net or near net shape (NNS) object, incontrast to subtractive manufacturing methods. Though “additivemanufacturing” is an industry standard term (ASTM F2792), AM encompassesvarious manufacturing and prototyping techniques known under a varietyof names, including freeform fabrication, 3D printing, rapidprototyping/tooling, etc. AM techniques are capable of fabricatingcomplex components from a wide variety of materials. Generally, afreestanding object can be fabricated from a computer aided design (CAD)model. A particular type of AM process uses electromagnetic radiation,such as a laser beam, to sinter or melt a powdered metal material,creating a solid three-dimensional object. Powder-based methods such asdirect metal laser melting (DMLM) and selective laser melting (SLM) havebeen used to produce objects for a variety of industries.

Selective laser sintering, direct laser sintering, selective lasermelting, and direct laser melting are common industry terms used torefer to producing three-dimensional (3D) objects by using a laser beamto sinter or melt a fine powder. For example, U.S. Pat. Nos. 4,863,538and 5,460,758 describe conventional laser sintering techniques. Moreaccurately, sintering entails fusing (agglomerating) particles of apowder at a temperature below the melting point of the powder material,whereas melting entails fully melting particles of a powder to form asolid homogeneous mass. The physical processes associated with lasersintering or laser melting include heat transfer to a powder materialand then either sintering or melting the powder material. Although thelaser sintering and melting processes can be applied to a broad range ofpowder materials, the scientific and technical aspects of the productionroute, for example, sintering or melting rate and the effects ofprocessing parameters on the microstructural evolution during the layermanufacturing process have not been well understood. This method offabrication is accompanied by multiple modes of heat, mass and momentumtransfer, and chemical reactions that make the process very complex.

FIG. 1 is schematic diagram showing a cross-sectional view of anexemplary conventional system 100 for direct metal laser sintering(DMLS) or direct metal laser melting (DMLM). The apparatus 100 buildsobjects, for example, the part 122, in a layer-by-layer manner bysintering or melting a powder material (not shown) using an energy beam136 generated by a source such as a laser 120. The powder to be meltedby the energy beam is supplied by a powder reservoir 126. The powderreservoir is also sometimes referred to as the powder dosing chamber.The powder is spread evenly over a build plate 114 using a recoater arm116 travelling in direction 134 to maintain the powder at a level 118and remove excess powder material extending above the powder level 118to waste container 128. The energy beam 136 sinters or melts a crosssectional layer of the object being built under control of the galvoscanner 132. The build plate 114 is lowered and another layer of powderis spread over the build plate and object being built, followed bysuccessive melting/sintering of the powder by the laser 120. The processis repeated until the part 122 is completely built up from themelted/sintered powder material.

Prior attempts to pack powder into the powder reservoir, or dosingchamber, have focused on leveling the bulk powder cone within thechamber. FIGS. 2-3 show two systems described in German PatentApplication DE 102012008664 A1. In FIG. 2, the cross-section of thecover plate 215 is adapted to the internal cross-section of the dosingchamber 203, which allows it to be placed into the dosing chamber 203.In this way, it can press the bulk cones in the interior of the dosingchamber, while avoiding excess powder being pushed out over the edgeregion of the dosing chamber when the cover plate flattens the bulkcone. Vibration can be introduced into the cover plate 215. In order tosmooth the surface of the building material, it is possible to providevibration elements on the cover plate 215. As soon as the uppermost partof the bulk cone has been removed due to the vibrating cover plate 215,the cover plate 215 is further inserted into the dosing chamber 203until the contact with the bulk cone again occurs. This allows the bulkcone to be graduated step by step.

FIG. 3 shows an alternative where a plurality of gas supply elements 318are arranged on the underside of the cover plate 315. The gas feedelements 318 have a lance shape so that they can be immersed in the bulkcone 317 formed from the building material. By introducing the gas intothe gas supply elements 318, the bulk cone 317 is whirled up and isthereby buried. For pressure compensation, an opening, which is sealedwith a filter, can be located in the cover plate 315, which openingseals the dosing chamber 303 in a powder-tight manner. Therefore, onlythe gas introduced into the dosing chamber 303 can leave the dosingchamber 303, but not the construction material 305. The gas supplyelements 318 are arranged with a particular advantage in a circularmanner; they can also consist of a plurality of concentric circles. Thecenter of these circles is the center of the outlet cone 316, the circleor the circles of gas supply elements 318 are arranged in such a waythat respectively below the opening of the cover plate 315 through whichthe building material 305 falls into the dosing chamber 303.

Such methods along with known manual powder packing methods, e.g., witha trowel, can result in non-uniform packing density within the powderreservoir. Moreover, these techniques are often slow and can lead tooperator fatigue and variation between batches. Accordingly, improvedsystems and method are needed to quickly and consistently pack powderinto the powder reservoir. Uniform packing density can also enableoperators to better plan for how much powder is needed; variability canlead to process disruption and wastefulness.

SUMMARY

The following presents a simplified summary of one or more aspects ofthe present disclosure in order to provide a basic understanding of suchaspects. This summary is not an extensive overview of all contemplatedaspects and is intended to neither identify key or critical elements ofall aspects nor delineate the scope of any or all aspects. Its purposeis to present some concepts of one or more aspects in a simplified formas a prelude to the more detailed description that is presented later.

In some aspects, the present disclosure is directed to a method forpreparing a powdered metal to be used in additive manufacturing,comprising steps a) to c). Step a) involves adding a first amount ofpowder to a powder reservoir. Step b) involves inserting a packing toolinto the powder reservoir to compact the powder, wherein the packingtool comprises a sleeve and a vibration source. Step c) involvesvibrating the packing tool to compact the powder in the powder reservoirand form a layer of compacted powder. In some aspects, the methodfurther comprises adding a second amount of powder over the layer ofcompacted powder. In some aspects, the powder reservoir comprises abottom plate, and the packing tool comprises a pressure sensor. In someaspects, vibrating the packing tool to compact the powder comprisesvibrating the packing tool and simultaneously raising the bottom plateat a velocity, until a predetermined pressure limit is reached. In someaspects, the method further comprises, before adding the first amount ofpowder into the powder reservoir, lowering the bottom plate. In someaspects, the packing tool is a top plate comprising the at least onemechanical member extending downward from the top plate. In someaspects, the method further comprises raising the top plate and rotatingthe top plate by 90°. In some aspects, the method further compriseslowering the top plate into the powder reservoir. In some aspects, themethod further comprises repeating the steps of: vibrating at least theat least one mechanical member and simultaneously raising the bottomplate at a velocity, until a predetermined pressure limit is reached;raising the top plate; rotating the top plate by 90°; and lowering thetop plate into the powder reservoir, until the top plate has rotated bya total of 360° relative to its original position. In some aspects, themethod further comprises, before step a), feeding the powder into afunnel and allowing the powder to flow from the funnel through one ormore tubes into the powder reservoir for an amount of time. In someaspects, the method further comprises, before allowing the powder toflow from the funnel through the one or more tubes into the powderreservoir, lowering the bottom plate. In some aspects, the methodfurther comprises, before allowing the powder to flow from the funnelthrough the one or more tubes into the powder reservoir, locking the topplate location over the top of the powder reservoir. In some aspects,the method further comprises, before allowing the powder to flow fromthe funnel through one or more tubes into the powder reservoir, the stepof raising the bottom plate until either the pressure sensor senses apowder packing limit, or the at least one mechanical member extendingdownward from the top plate contacts the bottom plate. In some aspects,the packing tool is inserted longitudinally into the powder reservoir.

In some aspects, the present disclosure is directed to an apparatus forpacking a powdered metal, comprising a vibration source; and at leastone mechanical member characterized by a variable frequency and variableintensity vibration; wherein the member is a sleeve configured toenvelop at least a portion of the vibration source; and wherein a clampengages a portion of the sleeve. In some aspects, the vibration sourceis electrically powered. In some aspects, the sleeve is removable fromthe vibration source. In some aspects, the apparatus further comprises atop plate comprising the at least one mechanical member extendingdownward. In some aspects, the top plate further comprises a pressuresensor. In some aspects, the at least one mechanical member comprises apressure sensor.

These and other aspects of the disclosure will become more fullyunderstood upon a review of the detailed description, which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary conventional powder bed apparatus for additivemanufacturing.

FIG. 2 shows a conventional powder packing apparatus including a coverplate.

FIG. 3 shows a conventional powder packing apparatus including gassupply elements.

FIG. 4A shows an example of an apparatus for powder packing according tothe present disclosure.

FIG. 4B shows a cross-sectional view of an exemplary packing tool foruse with the present disclosure.

FIG. 4C shows an alternate example of an apparatus for powder packingaccording to the present disclosure.

FIGS. 5A-5C show a schematic of a method of powder packing according tothe present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known components are shown in blockdiagram form in order to avoid obscuring such concepts.

The present application is directed to automated methods of preparingpowder to be used in additive manufacturing. Such methods differ fromconventional powder preparation methods by removing manual force andnon-standardized equipment and procedures. By automating the powderpacking process, the present disclosure improves processstandardization, reduces physical wear on the operator, and improvesmachine turnaround time (e.g., by minimizing preparation time).

FIG. 4A shows an example of an apparatus for use according to thepresent disclosure. A first amount of powder 406 is added to powderreservoir 404. In some aspects, powder reservoir may comprise a bottomplate 405. The powder reservoir 404 may be defined by one or moresidewalls 414 and a bottom plate 405. In one aspect, the bottom plate405 moves in a vertical direction. That movement may be facilitated inany known manner. In some aspects, bottom plate 405 is an external plateadded to the powder based additive manufacturing apparatus to furtherlimit the size of the powder reservoir 404.

In some aspects, bottom plate 405 may be lowered into a powder reservoir404 before adding powder to reservoir 404. Packing tool 410, comprisinga vibration source 401 and at least one mechanical member 402 extendingdownward, may be inserted into the powder-containing reservoir 404 andvibrated, to compact the powder in the reservoir 404 and form a layer ofcompacted powder (not shown). The at least one mechanical member 402 isa sleeve configured to envelop vibration source 401. The outer surfaceof the sleeve is made from a metal selected from cobalt chrome,stainless steels, tooling steel, maraging steel, aluminum alloys, nickelalloys, copper alloys, or titanium alloys. In some aspects, the outersurface of the sleeve is made of a metal that is the same as thepowdered metal used with the apparatus, to prevent contamination. Insome aspects, the packing tool 410 may further comprise one or morepressure sensors (not shown). The apparatus may further comprise avibration isolation ring (not shown) around the at least one mechanicalmember 402, and the vibration isolation ring may help damp and/orisolate vibrations and localize them to the packing tool 410. In someaspects, the sleeve may be removable from the vibration source andinterchangeable. After compacting the first amount of powder, a secondamount of powder may be added over the layer of compacted powder, andthe process may be repeated.

FIG. 4B shows a longitudinal cross-sectional view of an exemplarypacking tool 410 for use with the apparatus and method of the presentdisclosure. Packing tool 410 comprises a vibration source 401 and atleast one mechanical member 402, which is a sleeve configured to envelopvibration source 401. The at least one mechanical member 402 may beconfigured to envelop vibration source 401 by clamp 411, which may inturn comprise one or more gripping mechanisms 412, such as one or moreteeth or lips, which may be complementary to one or more grippingmechanisms (not shown) on the sleeve, and one or more fasteners 413,such as screws or nuts and bolts. In some aspects, clamp 411 comprisesone or more gripping mechanisms 412, such as teeth, configured to engageone or more gripping mechanisms of the sleeve. In some aspects, packingtool 410 is inserted, immersed, or submerged into powder-containingreservoir 404 (FIG. 4A) to a depth of no greater than the length of theat least one mechanical member 402. In some aspects, the packing tool410 is inserted, immersed, or submerged into powder-containing reservoir404 (FIG. 4A) to a depth greater than the length of the at least onemechanical member 402. Clamp 411 may be the made of the same or adifferent material than the metal powder. If the packing tool 410 is tobe inserted, immersed, or submerged into the powder-containing reservoir404 to a depth greater than the length of the at least one mechanicalmember 402, then it is preferable that the claim 411 is made of the samematerial as the metal powder.

The vibration source 401 may be any suitable source and may becommercially available. Non-limiting examples of suitable vibrationsources include, but are not limited to, Dewalt pencil vibrators andconcrete vibrators.

FIG. 4C shows an alternate example of an apparatus for use according tothe present disclosure. In some aspects, packing tool 410 comprises topplate 400 and at least one mechanical member 402 that is a sleeveconfigured to envelop a vibration source (not shown). A first amount ofpowder 406 is added to powder reservoir 404, which may comprise a bottomplate 405. In some aspects, the powder may be added via a funnel (notshown) and one or more tubes 403 running from the funnel. In someaspects, the powder may be allowed to flow from the funnel through oneor more tubes 403 into the powder reservoir 404 for an amount of time.In some aspects, the one or more tubes 403 may be open or closed. Insome aspects, bottom plate 405 may be lowered into a powder reservoir404 before allowing powder to flow from the funnel through one or moretubes into the reservoir 404. Packing tool 410 may be inserted into thepowder-containing reservoir 404 and vibrated, to compact the powder inthe reservoir 404 and form a layer of competed powder (not shown). Theapparatus may further comprise a vibration isolation ring (not shown)around the one or more tubes 403, and the vibration isolation ring mayhelp damp and/or isolate vibrations and localize them to the packingtool 410. After compacting the first amount of powder, a second amountof powder may be added over the layer of compacted powder, and theprocess may be repeated.

Packing tool 410 may further comprise one or more pressure sensors (notshown). In some aspects, the location of the top plate 400 or thepacking tool 410 may be locked over the top of powder reservoir 404before allowing powder to flow from the funnel (not shown) through theone or more tubes 403 into the powder reservoir 404. In some aspects,the one or more tubes 403 run from the funnel to the center of the topplate 400. In some aspects, the one or more tubes 403 run from thefunnel to the center and one or more corners of the top plate 400. Insome aspects, before allowing the powder to flow from the funnel throughthe one or more tubes 403 into the powder reservoir 404, the bottomplate 405 may be raised until either the one or more pressure sensorssense a powder packing limit or the at least one mechanical member 402extending downward from top plate 400 contact bottom plate 405.

The at least one mechanical member 402 may extend any length; it iswithin the knowledge of those of ordinary skill in the art to determineappropriate lengths for the at least one mechanical member 402. In someaspects, the at least one mechanical member 402 extends downward frompacking tool 410 by a length that is a function of the height of thepowder reservoir 404. For example, a taller powder reservoir 404 or ataller powder height may be used with a packing tool 401 with a longerat least one mechanical member 402. For example, the ratio of the heightof the powder reservoir 404 to the length of the at least one mechanicalmember 402 may range from 4:1 to 8:1, or any ratio in between. The atleast one mechanical member 402 is preferably suited to transmitvibration from the packing tool 410 to the underlying powder. In oneembodiment, the vibration is transmitted through cylindrical mechanicalmembers 402. The shape of the at least one mechanical member 402 mayalso be another shape, such as square or rectangular.

The powder reservoir 404 may be of any dimensions suitable for use withthe present method and apparatus. In some aspects, the powder reservoir404 has a rectangular or square base with sidewalls rising from theedges of the base. In some aspects, the powder reservoir 404 has a wallheight of no more than 4 feet. In some aspects, the powder reservoir 404has a wall height of no more than 3 feet. In some aspects, the powderreservoir 404 has a rectangular or square base measuring no less than 1foot long on at least one side. In some aspects, the powder reservoir404 has a square base measuring no more than 5 feet long on at least oneside.

The at least one mechanical member 402, that is a sleeve configured toenvelop a vibration source, may be of any sleeve wall thickness, whichis the difference between the outer and inner radii of the mechanicalmember 402. In some aspects, the at least one mechanical member 402 hasa sleeve wall thickness of no greater than 1.5 inches. In some aspects,the at least one mechanical member 402 has a sleeve wall thickness of noless than 0.25 inches.

The at least one mechanical member 402 may comprise any number ofmechanical members 402, or any array number. In some aspects, the numberof mechanical members 402 is a function of the width and/or depth of thepowder reservoir 404. In some aspects, the number of mechanical members402 is a function of the thickness (outer diameter) of the at least onemechanical member 402. For example, the smaller the thickness (outerdiameter) of the at least one mechanical member 402, the greater thenumber of mechanical member 402. Without wishing to be bound to anyparticular theory, it is believed that there may be an attenuation zonearound each vibration transmission element that provides improved powderpacking capabilities relative to the use of a vibrating plate alone. Inaddition, the present invention provides improved powder packing withoutintroduction of gas or any other means of powder packing, such as manualpacking with a trowel.

FIGS. 5A-5C show a schematic of steps of using the apparatus of thepresent disclosure, according to some aspects. In FIG. 5A, packing tool410 is lowered into powder reservoir 404, which contains a first amountof powder 406, which typically has a bulk powder cone formed by thepouring action. As packing tool 410 is lowered, the at least onemechanical member 402 becomes immersed in the first amount of powder 406(FIG. 5B). Once immersed to a desired depth, the packing tool 410 isvibrated, and the at least one mechanical member 402 transmits thevibrations down into the powder. In some aspects, the top plate 400 isvibrated while being lowered. In some aspects, the top plate 400 islowered while the bottom plate 405 is simultaneously raised. The atleast one mechanical member 402 may be vibrated while simultaneouslyraising the bottom plate 405 at a velocity, until a predeterminedpressure limit is reached, as detected by the one or more pressuregauges (not shown). In some aspects, the pressure limit and/or thevelocity at which the bottom plate 405 is raised may be controlled usinga computer. The at least one mechanical member 402 is believed to extendvibration down into the powder between top plate 400 and bottom plate405. The use of a predetermined pressure limit may improve consistencyin powder packing. Vibration may be at any suitable frequency and forany suitable duration of time.

After a suitable or desired vibration duration, the packing tool 410 maybe raised out of powder reservoir 404 (FIG. 5C). Packing tool 410 may beraised, rotated by 90°, and lowered into the powder reservoir 404. Thesteps of vibrating the at least one mechanical member 402 andsimultaneously raising the bottom plate 405 at a velocity until apredetermined pressure limit is reached, raising the packing tool 410,rotating the packing tool 410 by 90°, and lowering the packing tool 410into the powder reservoir 404 may be repeated. In some aspects, thesteps pack an amount of powder between top plate 400 and bottom plate405. In some aspects, the steps may be repeated until the packing tool410 has rotated by a total of 360°or a multiple thereof relative to itsoriginal position. In some aspects, the packing tool 410 is rotated by360°or a multiple thereof relative to its original position, such thatany holes created in the powder by the at least one mechanical member402 are filled in by powder during or as a result of the rotation(s).

In some aspects, a computer may also be used to control movements of thepacking tool 410, initiation of powder feed into a funnel (not shown),initiation of vibration of the at least one mechanical member 402, andraising or lowering of bottom plate 405. Raising and lowering of topplate 400, packing tool 410, and/or bottom plate 405 may be by anysuitable distance(s); determining such distance(s) is within theknowledge of those of ordinary skill in the art.

In some aspects, the apparatus comprises a funnel (not shown) one ormore tubes 403, a vibration isolation ring (not shown), and packing tool410, and may be separable from powder reservoir 404. The apparatus maybe separable from or joinable to the powder reservoir 404 by anysuitable means known to those of ordinary skill in the art.

The apparatus, funnel, one or more tubes 403, vibration isolation ring,packing tool 410, top plate 400, at least one mechanical member 402,powder reservoir 404, bottom plate 405, and one or more pressure sensorsmay be composed of any suitable materials known in the art, including,but not limited to, cobalt chrome. Preferably, parts that may come intocontact with the powder, such as the funnel, one or more tubes 403,packing tool 410, top plate 400, at least one mechanical member 402, oneor more pressure sensors, powder reservoir 404, and bottom plate 405, donot contaminate the powder. In addition, the apparatus, funnel, one ormore tubes 403, vibration isolation ring, packing tool 410, top plate400, at least one mechanical member 402, powder reservoir 404, bottomplate 405, and one or more pressure sensors are preferably made ofmaterials that can withstand vibration at the frequency and durationused according to the present disclosure.

The methods and apparatus of the present disclosure may be used with anypowder-based additive manufacturing methods and apparatuses, such asDMLM or SLM. The methods and apparatus of the present disclosure may beused with any powder material; preferably, the powder does not reactwith the material(s) from which the apparatus is made.

This written description uses examples to disclose the invention,including the preferred embodiments, and also to enable any personskilled in the art to practice the invention, including making and usingany devices or systems and performing any incorporated methods. Thepatentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those skilled in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal language of the claims.Aspects from the various embodiments described, as well as other knownequivalents for each such aspect, can be mixed and matched by one ofordinary skill in the art to construct additional embodiments andtechniques in accordance with principles of this application.

1. A powder packing apparatus for use in a powder-based additivemanufacturing system, the powder packing apparatus comprising: avibration source; and at least one mechanical member characterized by avariable frequency and variable intensity vibration; wherein the atleast one mechanical member is a sleeve configured to envelop at least aportion of the vibration source; and wherein a clamp engages a portionof the sleeve.
 2. The powder packing apparatus of claim 1, wherein thevibration source is electrically powered.
 3. The powder packingapparatus of claim 1, wherein the sleeve is removable from the vibrationsource.
 4. The powder packing apparatus of claim 1, further comprising atop plate comprising the at least one mechanical member extendingdownward from the top plate.
 5. The powder packing apparatus of claim 4,wherein the top plate further comprises a pressure sensor.
 6. The powderpacking apparatus of claim 1, wherein the at least one mechanical membercomprises a pressure sensor.
 7. The powder packing apparatus of claim 1,wherein the sleeve is made from a metal material.
 8. The powder packingapparatus of claim 7, wherein the metal material of the sleeve and apowder material of the powder-based additive manufacturing system arelike materials.
 9. The powder packing apparatus of claim 7, wherein themetal material of the sleeve and a powder material of the powder-basedadditive manufacturing system are different materials.
 10. The powderpacking apparatus of claim 7, wherein the metal material is selectedfrom cobalt, chrome, stainless steels, tooling steel, maraging steel,aluminum alloys, nickel alloys, copper alloys, or titanium alloys. 11.The powder packing apparatus of claim 1, wherein the clamp comprises oneor more gripping mechanisms.
 12. The powder packing apparatus of claim1, wherein the clamp comprises one or more fasteners.
 13. The powderpacking apparatus of claim 1, wherein the clamp and a powder material ofthe powder-based additive manufacturing system are made of likematerials or are made of different materials.
 14. The powder packingapparatus of claim 1, wherein a powder material of the powder-basedadditive manufacturing system is contained in a reservoir.
 15. Thepowder packing apparatus of claim 14, further comprising a top platecomprising the at least one mechanical member extending downward fromthe top plate into the reservoir containing the powder material.
 16. Thepowder packing apparatus of claim 14, wherein the reservoir comprises abottom plate, and wherein the powder packing apparatus comprises apressure sensor.
 17. The powder packing apparatus of claim 14, whereinthe sleeve and the powder material are selected from cobalt, chrome,stainless steels, tooling steel, maraging steel, aluminum alloys, nickelalloys, copper alloys, or titanium alloys.
 18. The powder packingapparatus of claim 13, wherein the clamp comprises one or more grippingmechanisms or one or more fasteners.
 19. The powder packing apparatus ofclaim 14, wherein the powder packing apparatus is a top plate comprisingthe sleeve and the vibration source extending downward from the topplate into the reservoir.
 20. The powder packing apparatus of claim 1,wherein the variable frequency and the variable intensity vibration arecontrolled by a computer.